The present invention relates to lighted exit signs and emergency signs, and, more particularly, to light units for such signs.
Exit signs and emergency signs are widely employed in commercial and industrial buildings as well as in multi-unit residential buildings to identify exits and provide other information to persons who may be within the structure. Some such signs are continuously illuminated, others are illuminated only in the event of emergencies such as the loss of power, and still others are illuminated by the building power supply normally and by battery power when building power is lost. Such signs are usually illuminated by two incandescent or compact fluorescent lamps, each of which will normally have a rating of 15-25 watts. The incandescent and fluorescent lamps results in a power requirement which becomes particularly significant when the signs are powered by a battery supply in the event of an emergency.
Recently, there have been efforts to utilize light emitting diodes (LEDs) to effect illumination of exit signs so as to reduce the amount of the power required, and such efforts have necessarily involved the use of a relatively large number of spaced light emitting diodes to provide the necessary candlepower for adequate illumination. In some such signs, the light emitting diodes have been oriented in rows corresponding to the configuration of the letters directly under which they are disposed. Because of this orientation, an undesirable result is that the light emitting diodes produce a multiplicity of bright spots in the illuminated legend of the sign even when diffuser material is placed between the LEDs and the legend sheet or plate.
Another substantial advantage to use of light emitting diodes in addition to the lower power consumption (an array may require only 2 watts), is that they generate less heat and are much longer lived. This also enables the reduction of the size and cost of DC power supplies for emergency power. Accordingly, there are decided advantages to employing LEDs if the objectionable point source effect can be overcome.
It is an object of the present invention to provide a novel light unit for exit and emergency signs incorporating light emitting diodes as the light source and providing diffuse illumination of the indicia of the sign legend.
It is also an object to provide such a light unit providing a substantially uniformly lighted appearance for the characters of the legend.
Another object is to provide such a light unit which can readily replace the incandescent and fluorescent light units in existing exit and emergency signs.
Still another object is to provide such a light unit which may be fabricated readily and economically from components which may be readily assembled.